1. Field
Exemplary embodiments relate generally to communications and more particularly to communications over power systems.
2. Related Art
Power line communication (PLC) refers to systems for carrying data on conductors typically used for electric power transmission. Alternative terminologies for PLC include power line carrier, mains communication, power line telecommunications (PLT) and power line networking (PLN).
In these systems, electrical power may be transmitted over high voltage transmission lines, distributed over medium voltage, and used inside buildings typically at lower voltages. Powerline communications can also be applied at each stage. Often, PLC systems are limited to a single set of wires, such as premises wiring, though there are systems which can cross between two levels, such as the distribution network and the premises wiring.
Typically, PLC systems operate by providing a modulated carrier signal on the wiring system. Different types of powerline communications may use differing frequency bands, depending on the signal transmission characteristics of the power wiring used. Power wire circuits have a limited ability to carry higher frequencies because power wiring systems were originally intended for transmission of AC power. The propagation problem is a limiting factor for each type of power line communications.
The data rates over power line communication systems may vary widely. For example, low-frequency (100-200 kHz) carriers on high-voltage transmission lines may carry one or two analog voice circuits, or alternatively, control and/or telemetry circuits with an equivalent data rate. Such circuits may be numerous kilometers long. Higher data rates are available, but generally have shorter ranges. For example, a local area network (LAN) may operate at megabits per second (Mbps) and would cover perhaps a single floor of a building.
Broadband over power lines (BPL) uses PLC by receiving and sending radio signals over power lines to provide access to the networks, such as the Internet. A BPL system may utilize, for example, the overhead medium voltage (MV) or low voltage (LV) power lines to transmit multi-Mbps data signals. However, these systems may suffer from some major drawbacks.
For one, as noted they have a limited range, after which a signal repeater is required. However, repeating the signals in an overhead power line environment, for example, is a problem as the regenerated signal interferes with the original signal and reduces the overall bandwidth.
Secondly, such systems are inherently unreliable. Their communications capability may be disrupted when a power line fails, for example, due to line faults, equipment malfunctions, failures caused by weather/lightning strike, overloaded transformers, blown fuses or other causes.
Consequently, utilities, and notably the electric utilities, need a reliable carrier class communications system with high availabilities, and which can reach longer distances in cities/suburbs and rural/remote areas. Such systems, and accompanying methods, are needed and desired to manage and control the millions of devices on the power distribution grid.